A bitterly divided San Francisco Board of Supervisors embroiled in mayoral politics and disagreement over policy rejected Supervisor Gavin Newsom's "Care Not Cash" welfare reform measure Tuesday, leaving it to the courts to decide whether the voter-backed plan should become law.

It was clear from the start that Newsom, who is running for mayor and has been accused of exploiting the homeless issue for political gain, wouldn't get Care Not Cash past a majority of his colleagues on the board.

Newsom fell one shy of the six votes he needed to win approval for the legislation that would cut city-funded cash welfare payments from as much as $410 a month for about 2,500 of San Francisco's homeless to as low as $59. The cash would be replaced with provisions of shelter, food and other city services.

"Today we rejected a fundamental notion that we can do better," Newsom said after the vote.

His comments also suggested a message that he'll use on the campaign stump: "I'm going to fight for change. I'm going to fight for the people of San Francisco."

Two rivals in the mayor's race, Supervisors Tom Ammiano and Matt Gonzalez, voted against the proposed law, saying it is based on false promises.

Dozens of homeless advocates crowded into the legislative chamber and jeered Newsom when he walked into the room and when he spoke. They jumped to their feet and cheered when the measure failed. At one point, sheriff's deputies cleared the room and engaged in a standoff with the boisterous but peaceful protesters who disrupted the meeting.

The legislative showdown came 10 months after nearly 60 percent of the city's voters approved the proposal. But a Superior Court judge struck down the ballot measure in May, saying that only the supervisors, not the electorate, could enact such a policy.

Newsom then brought the proposal to the board for consideration, but after considerable debate and delays it was turned down. Meanwhile, the city attorney has appealed the court ruling, keeping the proposal alive. A ruling is most likely several months away.

Opponents said Care Not Cash would not be able to live up to voters' expectations that adequate services would be provided to the homeless people whose cash aid would be cut. Critics pointed to a report by Board of Supervisors Budget Analyst Harvey Rose that raised doubt over whether the money would be available to pay for the anticipated services. Debate also raged over what types of services would be offered -- for example, stable housing or a shelter bed.

"When we look at it, when our budget analyst looks at it, we know the promises will be unfulfilled . . ." said Gonzalez. "If the numbers don't add up, I don't think we should be forcing it and pretend that it works."

Trent Rhorer, the city's welfare chief who helped craft Care Not Cash, said that the numbers do add up and that there would be money to house at least 1, 000 more people in residential hotel rooms -- a step up from a cot in an emergency shelter -- and to add hundreds of more treatment slots for the drug- addicted and alcoholics.

"We feel we're able to implement Care Not Cash," Rhorer said.

The money, he said, would come from a projected drop-off in the welfare rolls if people no longer get a full cash grant, and in the savings from having to pay a smaller cash stipend.

But Budget Analyst Rose called the funding plan "a back-of-the-envelope- type document" full of inconsistencies.

That was enough of an argument for Supervisor Tony Hall, who indicated that he and other supervisors who oppose Care Not Cash had the opportunity to study the details and know better than voters.

"I will protect the constituents in my district who didn't have the advantage of reading the fine print or really know what they were voting for," said Hall, who represents the traditionally moderate to conservative west of Twin Peaks neighborhoods in District 7. Voters in District 7 voted heavily in favor of Care Not Cash last November.

Prompted by the Care Not Cash win at the ballot, the Board of Supervisors in July approved an alternative version written by Daly that for the first time moves the city away from a cash-based system of care. Dubbed "Real Housing, Real Care," the plan is similar to Care Not Cash in that it replaces a big chunk of the cash stipend with services.

However, it mandates that the check cannot be reduced until the homeless person is provided with a room in a residential hotel or a slot in a residential treatment program. Rhorer estimates that about 1,000 people would be affected, or fewer than half targeted by Care Not Cash.